Anatomy & Physiology I and II

Anatomy & Physiology Study Guide

©2018 Achieve Test Prep Page 130 of 367 Functions The basal nuclei are encompassed with the subconscious influence of skeletal muscle tone and the coordination of acquired movement patterns. Under standard conditions, these nuclei do not originate particular movements. But once a movement is under way, the basal nuclei provide the usual pattern and rhythm, particularly for movements of the trunk and proximal limb muscles. Information arrives at the caudate nucleus and putamen from sensory, motor, and integrative areas of the cerebral cortex. Processing occurs in these nuclei and in the bordering globus pallidus. A large majority of the productivity of the basal nuclei leaves the globus pallidus and synapses in the thalamus. Nuclei in the thalamus then project the information to appropriate areas of the cerebral cortex. The basal nuclei alter the motor commands issued by the cerebral cortex through this feedback loop. 12.8 Motor and Sensory Areas of the Cortex The central sulcus divides the motor and sensory sections of the cortex. The precentral gyrus of the frontal lobe creates the anterior border of the central sulcus. The surface of this gyrus is the primary motor cortex. If a specific motor neuron in the primary motor cortex is stimulated, it generates a contraction in a specific skeletal muscle. Like the monitoring gauges, the sensory areas of the cerebral cortex report key information. At each location, sensory information is reported in the pattern of neuron activity in the cortex. The postcentral gyrus of the parietal lobe creates the posterior border of the central sulcus, and its surface contains the primary sensory cortex. Receptors for touch, vibration, pressure, taste, pain, or temperature send somatic sensory information to the neurons of the postcentral gyrus. Sensations of sight, sound, smell, and taste arrive at other portions of the cerebral cortex. The visual cortex of the occipital lobe obtains visual information, and the auditory cortex and olfactory cortex of the temporal lobe collect information about hearing and smell. The gustatory cortex collects information from taste receptors of the pharynx and tongue. 12.9 Association Areas The sensory and motor areas of the cortex are attached to nearby association areas, or regions of the cortex, that interpret incoming data or coordinate a motor response. Sensory association areas are cortical regions that monitor and decipher the information that arrives at the sensory areas of the cortex. Examples include the somatic sensory association area, visual association area, and auditory association area. The special senses of smell, sight, and hearing involve separate areas of the sensory cortex, and each has its own association area. These areas monitor and interpret arriving sensations. The somatic motor association area, or premotor cortex , is responsible for the coordination of learned movements. When a voluntary movement is performed, the instructions are relayed to the primary motor cortex by the premotor cortex. With repetition, the proper pattern of stimulation becomes stored in the premotor cortex. Then the movement can be performed smoothly and effortlessly by triggering the pattern rather than by controlling the individual neurons.